Electromechanical oscillator



Augc. F. CLIFFORD 3,522,500 I ELECTROMECHANICAL OSCILLATOR Filed June 20, 1967 g: CECIL] FRANK CLIFFORD United States Patent 3,522,500 ELECTROMECHANICAL OSCILLATOR Cecil Frank Clifford, Newbridge Works,

Bath, Somerset, England 2 Filed June 20, 1967, Ser. No. 647,396 Claims priority, application Great Britain, July 6, 1966, 30,255/ 66 Int. Cl. H02k 33/00 US. Cl. 318-428 3 Claims ABSTRACT OF THE DISCLOSURE Electromechanical oscillator in which a single oscillating member or the tines of a tuning fork, cooperate inductively with signal and drive coils connected to an amplifier by which the member or the fork is maintained in oscillation, and also cooperate magnetically with a wavy magnetic track formed on an escape Wheel so that the escape wheel is driven by the oscillating member or the tuning fork.

This invention relates generally to electromechanical oscillators of the type which may have one or two mechanically oscillating members, an oscillating reed being an ex ample of an oscillator having one oscillating member, a tuning fork being an example of an oscillator which has two oscillating members, the reed or tuning fork being maintained in oscillation by electrical means.

Oscillators of the type defined above are becoming increasingly improtant. They are being applied to the control of clocks and timing mechanisms, and even to form the timekeeping mechanism in electrically operated wrist watches. Economy and compactness in the design and construction of such oscillators is therefore becoming increasingly important and the principal object of the invention is to provide an oscillator in which the or each oscillating member performs a dual function in co operating inductively with a coil connected to an amplifier and in magnetically causing the rotation of an escape wheel by which the oscillations of the oscillating member or members are converted to rotary motion which may be employed to drive the hands of a clock or to control some other kind of timing mechanism.

The invention consists of an electromechanical oscillator comprising one or two mechanically oscillating members, the or each oscillating member constituting or being provided with a magnetic member, and escape Wheel having on at least one face thereof a wavy magnetic track, and at least one coil for connection to an amplifier, in which the or each magnetic member is so arranged that it cooperates inductively with a coil and cooperates magnetically with the escape wheel to cause the rotation thereof.

Where the oscillating member is a tuning fork a magnet may be mounted on the end of each tine, the outer end of each magnet cooperating inductively with an associated coil and the inner end of each magnet, between the tines, being formed at its end to cooperate with the wavy magnetic track. Conveniently a magnetic or magnetizable pin may be fixed to the inner end of each magnet projecting towards the wavy track formed on one face of the escape wheel.

In another arrangement a single fixed magnet may be mounted between the tines of the fork carrying a fixed amplifier coil, the tines of the fork acting as magnetic inductors which, as they move, induce impulses in the coil, and also being arranged to cooperate with opposite points of a wavy magnetic track formed on one face of the escape wheel. In another arrangement a single fixed magnet and coil may be employed and each magnetic inductor carries an extension arranged to cooperate with 3,522,500 Patented Aug. 4, 1970 separate wavy magnetic tracks formed on opposite sides of the escape wheel.

A magnetic escapement in which an escape wheel is formed on both faces with an undulating or wavy mag netic track and an oscillating magnetic reed which is bifurcated and straddles a part of the wheel, and is formed with inturned magnetic pole tips which are close to the respective tracks in such a way as to control the rotation of the wheel, is in itself known. In such a magnetic escapement the escape wheel itself may be driven, as by a spring or electric motor, in which case the rate of rotation of the, wheel is controlled by the rate of oscillation of the reed. Alternatively the oscillation of the reed may be caused to drive the escape wheel, which may in turn be geared to a timing mechanism such as a clock.

Selected embodiments of the invention will be described by way of example with reference to the accompanying drawings, in which- FIG. 1 shows one embodiment of the invention;

FIG. 2 shows an alternative embodiment; and

FIG. 3 shows a further embodiment.

FIG. 1 shows a lateral section through the two tines, respectively 11 and 12, of a tuning fork. A magnet 13 is mounted on one end of the tine 11 and a magnet 14 is mounted on one end of the tine 12, the two magnets being centrally disposed with respect to the associated tines. The outer end of the magnet 13 lies within a coil 15 and the outer end of the magnet 14 lies with a coil 16. The two coils 15 and 16 are adapted for connection to an amplifier, which may consist of a single transistor, one coil being connected in the amplifier input circuit and the other coil being connected in the amplifier output circuit, so that impulses induced in the one coil due to the vibration of the associated magnet cause amplified impulses to appear in the other coil which maintain the tuning fork in vibration. The use of an amplifier in this manner is Well known.

Attached to the inner end of the magnet 13 is a pin 17 made of a magnetic material such as soft iron, and attached to the inner end of the magnet 14 is a further pin 18 made of similar'material. If it is desired to augment the power of the magnets attached to the tines of the fork the pins 17 and 18 may themselves be permanent magnets. An escape wheel 19 is formed upon its face nearest the magnets with a wavy magnetic track, which may be produced either by stamping pieces out of the disc to leave the track or by forming a raised track on the escape wheel face as described, for example, in my copending patent application Ser. No. 643,933 filed June 6, 1967. The wheel 19 is mounted on a spindle 20 which is supported in pivot bearings, respectively 21 and 22.

In order to maintain the tuning fork in continuous oscillation a conventional transistorized maintainig circuit may be employed, as indicated schematically in FIG. 1. One end of the coil 16 is connected to the input of the amplifier and the output of the amplifier is connected to one end of the coil 15. The remaining ends of the tWo coils are connected together and to a lead 34 which is connected to the earth or ground terminal of the amplifier.

In operation, the vibration of the tines of the tuning fork causes the rotation of the escape wheel 19, so that the speed of the escape wheel is directly dependent upon the frequency of oscillation of the tines 11 and 12. The spindle 20 may be connected by gearing (not shown) or by other means such that the rotation of the wheel 19 controls the operation of a clock or timing mechanism.

The use of the magnetic pins 17 and 18 mounted on the inner ends of the magnets 13 and 14 is only one example of the use of the invention. It will be understood that, if desired, the ends of the magnets themselves could be suitably formed or shaped to cooperate directly with the magnetic track on the escape wheel 19.

In FIG. 2 a single fixed magnet 23 is employed and this has a coil 24 mounted upon it. In the kind of oscillator being discussed two coils are sometimes employed as indicated in FIG. '1, one of the coils being connected in the input circuit and the other in the output circuit of the amplifier. One end of each coil is connected to the earth or ground line of the amplifier and this in turn is connected either to the positive or the negative pole of the power supply (depending on whether a p-n-p or an n-p-n transistor is used) and since one end of each coil is connected to the ground line a single tapped coil may be employed instead of two separate coils.

Reverting to FIG. 2, the tines of the tuning fork are used as inductors or carry inductors, respectively 25 and 26. The inductor 25 is fitted with a projecting pin 27 while the inductor 26 is fitted with a similar pin 28. The pins 27 and 28 are made of magnetic material such as soft iron or a low loss magnetic alloy, and they co-operate with a wavy magnetic track of known type formed on one face of an escape wheel 29. The shape and arrangement of the wavy magnetic track may be seen, for example, in our copending patent applicationNo. 29,905/66 already referred to. Since the two tines of the fork move alternately towards and away from each otherit will be evident that the wavy magnetic track must have an even number of waves arranged around the face of the escape wheel 29.

FIG. 3 shows a further arrangement according to the invention. In this arrangement also a fixed magnet 23 and a fixed coil 24 surrounding the magnet are employed and the tines of the fork either constitute, or are provided with, magnetic inductors 30 and 31. The escape wheel 32 is provided with a wavy magnetic track on both faces. The magnetic inductor 30 is fitted with a shaped member 31 which may be made from a rod of magnetic material such as soft iron and the inductor 33 is fitted with a further shaped member 34, the members 33 and 34 being shaped to cooperate respectively with two wavy magnetic tracks on the opposite faces of the escape wheel 32. Since the ends of the tines of the fork'are alternately moving towards and away from each other it will be evident that the two wavy magnetic tracks must be phase-disp1aced from each other in the rotational direction of the wheel by one-half wave.

It is to be understood that the exercise of the invention is not confined to the particular embodiments which have been illustrated and described, and other arrangements may be devised within the scope of the appended claims.

What is claimed is:

1. An electromechanical oscillator comprising a tuning fork, a magnet mounted on the end of each tine of the fork, an escape wheel having on at least one face thereof a wavy magnetic track, two coils for connection to an amplifier, the outer end of each magnet cooperating inductively with one coil for maintaining oscillation of the fork, the inner end of each magnet, between the tines, being formed at its end to cooperate with the wavy magnetic track to cause rotation of the escape wheel as the fork oscillates. v

2. An oscillator as claimed in claim 1 comprising a magnetic or magnetizable pin fixed to the inner end of each magnet projecting towards the wavy magnetic track to cooperate therewith.

3. An electromechanical oscillator comprising a tuning fork, a fixed magnet mounted between the tines of the fork, a fixed coil carried on the magnet for connection to an amplifier, the tines of the fork being arranged to act as magnetic inductors, an escape wheel having wavy magnetic tracks formed on both faces thereof, the two wavy magnetic tracks being phase displaced by one half wave with respect to each other in the'direction of rotation of the escape Wheel, and an extension on each inductor so shaped that the inductors cooperate respectively with the wavy magnetic tracks on the two faces of the escape wheel to cause rotation of the escape wheel as the fork oscillates.

References Cited UNITED STATES PATENTS 

